Help with 91 GT fueldampers

[Pefa]

Hi.

A friend has a 91 GT that is hard to start when warm.
I checked fuelpressure and it bleeds of after shutdown. I took the vacuum connection off of the FPR and there was gas in the vacuumline. I guess this means 1 or both of the fueldampers are shot?
I need help eliminating which part is fualty.

Advise please
// Peder

[Tom]

Hi.

A friend has a 91 GT that is hard to start when warm.
I checked fuelpressure and it bleeds of after shutdown. I took the vacuum connection off of the FPR and there was gas in the vacuumline. I guess this means 1 or both of the fueldampers are shot?
I need help eliminating which part is fualty.

Advise please
// Peder

Chances are the bad one won't hold vacuum. If you have a little MityVac or similar tool, I'm guessing the bad one will be obvious (assuming the fuel is coming from one of them).

[Pefa]

Hi.

A friend has a 91 GT that is hard to start when warm.
I checked fuelpressure and it bleeds of after shutdown. I took the vacuum connection off of the FPR and there was gas in the vacuumline. I guess this means 1 or both of the fueldampers are shot?
I need help eliminating which part is fualty.

Advise please
// Peder

Chances are the bad one won't hold vacuum. If you have a little MityVac or similar tool, I'm guessing the bad one will be obvious (assuming the fuel is coming from one of them).

Yes I can test if they hold vacuum. If one of them cant hold vacuum Is there a procedure to bridge a fualty fueldamper to see if fuelpressure holds after shutdown?

[Tom]

Hi.

A friend has a 91 GT that is hard to start when warm.
I checked fuelpressure and it bleeds of after shutdown. I took the vacuum connection off of the FPR and there was gas in the vacuumline. I guess this means 1 or both of the fueldampers are shot?
I need help eliminating which part is fualty.

Advise please
// Peder

Chances are the bad one won't hold vacuum. If you have a little MityVac or similar tool, I'm guessing the bad one will be obvious (assuming the fuel is coming from one of them).

Yes I can test if they hold vacuum. If one of them cant hold vacuum Is there a procedure to bridge a fualty fueldamper to see if fuelpressure holds after shutdown?

If one is bad, then I'd think you replace it (since you'd need to replace anyway) and see if that fixes the bleed off issue. You could probably pinch lines to isolate the bleed down, but chances are whatever is leaking fuel into the vacuum lines is causing the bleed-off. That said, I'm out of my element with the 928, so hopefully @dr bob or @Gregbbrd see this and give you better informed advice.

p.s., get your friend to sign up on Carpokes. We need more 928ers....

[Pefa]

Chances are the bad one won't hold vacuum. If you have a little MityVac or similar tool, I'm guessing the bad one will be obvious (assuming the fuel is coming from one of them).

Yes I can test if they hold vacuum. If one of them cant hold vacuum Is there a procedure to bridge a fualty fueldamper to see if fuelpressure holds after shutdown?

If one is bad, then I'd think you replace it (since you'd need to replace anyway) and see if that fixes the bleed off issue. You could probably pinch lines to isolate the bleed down, but chances are whatever is leaking fuel into the vacuum lines is causing the bleed-off. That said, I'm out of my element with the 928, so hopefully @dr bob or @Gregbbrd see this and give you better informed advice.

p.s., get your friend to sign up on Carpokes. We need more 928ers....

I checked prices and one is 450usd and the other is 700usd crazy prices!

I see about my friend, not into phones and computers but ill check

[dr bob]

On your friend's '91 GT, there is one FPR (right rear position) and two fuel pressure dampers (Front center/right and left rear). As you discovered, the pieces are pretty expensive buying from Porsche these days. The good news is that a few folks the US have been working on replacements that use a drop-in Bosch "cartridge", for less money and with future rebuilds possible. The cartridges are common in many M-B cars, so they are relatively future-proof. The FPR is also common to some 964 cars.

Greg Brown sells them I think. There are other versions sold by non-members, but we try to support our members first given that option. I'll Ping Greg now in case he doesn't cruise through here on his own.

[Pefa]

On your friend's '91 GT, there is one FPR (right rear position) and two fuel pressure dampers (Front center/right and left rear). As you discovered, the pieces are pretty expensive buying from Porsche these days. The good news is that a few folks the US have been working on replacements that use a drop-in Bosch "cartridge", for less money and with future rebuilds possible. The cartridges are common in many M-B cars, so they are relatively future-proof. The FPR is also common to some 964 cars.

Greg Brown sells them I think. There are other versions sold by non-members, but we try to support our members first given that option. I'll Ping Greg now in case he doesn't cruise through here on his own.

Thanks for sharing!

I tested today with a mityvac and all 3 held vacuum while pumping up pressure. However when I bypassed the fuelpump and with the vacuum lines disconnected, fuel poored out of all three units vacuum ports!!

To me this means all 3 are defective correct?

A less expensive solution to these units would be much appreciated.

However me being in Sweden, VAT, shipping and customs adds up so interested to know the prices of those alternative units.

Thanks
Peder

[Tom]

On your friend's '91 GT, there is one FPR (right rear position) and two fuel pressure dampers (Front center/right and left rear). As you discovered, the pieces are pretty expensive buying from Porsche these days. The good news is that a few folks the US have been working on replacements that use a drop-in Bosch "cartridge", for less money and with future rebuilds possible. The cartridges are common in many M-B cars, so they are relatively future-proof. The FPR is also common to some 964 cars.

Greg Brown sells them I think. There are other versions sold by non-members, but we try to support our members first given that option. I'll Ping Greg now in case he doesn't cruise through here on his own.

Thanks for sharing!

I tested today with a mityvac and all 3 held vacuum while pumping up pressure. However when I bypassed the fuelpump and with the vacuum lines disconnected, fuel poored out of all three units vacuum ports!!

To me this means all 3 are defective correct?

A less expensive solution to these units would be much appreciated.

However me being in Sweden, VAT, shipping and customs adds up so interested to know the prices of those alternative units.

Thanks
Peder

Did the fuel pour out like they had an on-going supply? Any chance one thing is leaking fuel into the vacuum lines and the gas just got into and filled up the vacuum side of all three diaphragms?

[Pefa]

On your friend's '91 GT, there is one FPR (right rear position) and two fuel pressure dampers (Front center/right and left rear). As you discovered, the pieces are pretty expensive buying from Porsche these days. The good news is that a few folks the US have been working on replacements that use a drop-in Bosch "cartridge", for less money and with future rebuilds possible. The cartridges are common in many M-B cars, so they are relatively future-proof. The FPR is also common to some 964 cars.

Greg Brown sells them I think. There are other versions sold by non-members, but we try to support our members first given that option. I'll Ping Greg now in case he doesn't cruise through here on his own.

Thanks for sharing!

I tested today with a mityvac and all 3 held vacuum while pumping up pressure. However when I bypassed the fuelpump and with the vacuum lines disconnected, fuel poored out of all three units vacuum ports!!

To me this means all 3 are defective correct?

A less expensive solution to these units would be much appreciated.

However me being in Sweden, VAT, shipping and customs adds up so interested to know the prices of those alternative units.

Thanks
Peder

Did the fuel pour out like they had an on-going supply? Any chance one thing is leaking fuel into the vacuum lines and the gas just got into and filled up the vacuum side of all three diaphragms?

Yes more like an ongoing supply. Broken diaphragms?

[Zirconocene]

I don't know if you got this fixed but I ended up coming up with some aftermarket parts from Radium that I was able to make work for the dampers and regulator.

Knowing what I know now, I think that there are Radium parts which could be made to be drop in parts for the Porsche OEM versions.

I can send you pictures, or if you want to look at what I posted on RL, I have some over there on my setup. I would do it differently if I were to do it again, but using the same parts.

Cheers